2009-06-03

Spirit Sol 149

The big poster outside my office is drooping. The duct tape that holds it up (can you tell we're engineers around here?) has come unstuck at one corner, and it's folded over itself. I don't want it to get damaged, so I stick it back up.

"What were we thinking when we dumped the HAFIQ?" I ask Chris as I walk into the sequencing MSA.

"What do you mean?"

The Hazard Avoidance Fault Image Queue is a buffer that contains the last few images the rover has taken as it proceeds on autonav. The idea is that if the rover encounters certain kinds of errors while driving, it automatically dumps the queue -- sending those images back to Earth -- so that we can see what's wrong. We've also gotten in the practice of adding commands to manually dump the HAFIQ at the end of a drive in other cases, because that gives us more data about the rover's surroundings when we need it most. Yestersol, we dumped the HAFIQ unconditionally.

But that was a dumb thing to do, because there was no autonav yestersol -- it was all blind driving. So there's nothing useful in the HAFIQ. All we'll get is some useless overhead data that comes down with the empty queue.

I point this out to Chris. "Oh," he says. Then he shrugs. "Well, it was just two megabits."

Which is actually a fair point. Early in the mission, I got in the habit of working to eliminate every unnecessary bit of downlink. We were packing every sol so full of science observations that anything we could save on the engineering side was significant -- it meant we could work in another science observation, and that's what we're here for, after all. Nowadays, with our less efficient planning process, there's a lot more slop. Also, we're now normally constrained by energy, not by data volume, and since we doubled our top data rate, we often have more available downlink data volume than we used to. So it doesn't matter so much any more.

I'm still going to cut it if this happens again. For old times' sake, if nothing else.

Yestersol's drive was successful. We ended up in a spot where we can deploy the IDD and poke at stuff -- including the magnets mounted at the base of the PANCAM mast, which is always fun because the rover's arm has to swing up over its own body. Some of the IDD observations are cut for time or energy reasons, but much remains.

As usual, I start my shift by independently reviewing the state of the rover while Chris charges ahead with the sequencing. While we're doing this, we hear a Labwide announcement: "Please join NASA administrator Sean O'Keefe for a discussion of exploration." "Sorry," Chris says, "we're too busy exploring."

"Yes and no," Bob shrugs. "It's definitely easier doing one job than two." Apparently, they're moving him out of the building -- Phoenix development is being moved into a trailer. You should have stayed on MER, Bob. Then again, when Cassini reaches Saturn (less than a month from now) and crowds us out of the news entirely, maybe we'll be moved into a trailer, too.

Bob also congratulates us on passing the 3km mark. Justin Maki says: "You know, we passed the 3km mark and nobody noticed. I brought it up in a meeting, and everybody was like, eh." But even if familiarity has bred contempt, it's still a hell of an achievement: we've now gone five times our required distance, and we're still zooming along. "Remember all the meetings where they were saying the 600m requirement was too much and we should take it out?" Justin remarks. He adds, though, that we're inadvertently making life harder for MSL. "MSL is like, before MER landed, we had all these requirements, and now MER has done half of them."

Aw, poor MSL. I can guarantee them one thing: we're not stopping any time soon, certainly not to make their jobs easier. They'll just have to deal.

Chris finishes with his part of the work, and we walk through the sequence together as part of the handover. Emily asks him for the estimated duration of one of the sequences, and he tells her.

"Does that include the 10-second-per-move overhead that RSVP doesn't model?" I ask him. This is overhead imposed by the IMU, which needs to go into the mode where it tracks the vehicle's attitude every time we move the IDD, and entering that mode takes a few seconds.

"No," he says, "remember, that's not needed any more because we're not using the IMU while moving the IDD now."

"Oh, right. Hey, if you wait long enough, the bug turns into a feature."

Emily forgets to have Chris sign the activity plan approval form before he leaves, so she asks me to sign it instead.

"I always wondered what would happen if I didn't sign one of these," I say.

"Nothing," she answers. "I forgot to do one yesterday."

Ah, we're a well-oiled machine.

Sounds like Opportunity's going into Endurance Crater. Squyres lets this slip as he's telling Mark Adler that Spirit might climb the hills -- "but keep it in the family," he says; it's not official yet, but the handwriting is on the (crater) wall.

Adler shakes his head as Steve leaves. "Those guys have been having meeting after meeting with high-level management about going into that crater," he says. "High-level" means, at least, Ed Weiler, the guy who's basically the NASA-side man in charge of JPL. Since entering the crater is a potentially mission-limiting decision -- once they go in, they may never get back out -- it had to get his approval. And apparently he's decided the scientists can have their way.

Steve pops back in to add, "We should figure out where we're going to winter" -- that is, where we want the rovers to be during the winter solstice, when solar energy will be at its lowest. Mark has clearly been thinking about this already. "We want to aim the solar panels north to maximize sun exposure," he says. "That's the great thing about hills -- you can find a way to aim pretty much wherever you want." If Opportunity's in the crater, it can pull the same trick -- climb partway up the south wall of the crater, so its solar panels are aimed north. And wait.

Art Thompson is working on Opportunity this month, but he stops by to keep in touch. This is Emily's last shift as TUL for a few days -- Julie Townsend is in tomorrow -- and Art asks if Emily has depleted Spirit's batteries. (This is part of an ongoing good-natured rivalry of sorts, where each team tries to leave the other in a difficult position.) "She's gonna have to drive it into the gas station?" Art asks.

"She's gonna have to push it into the gas station!" Emily says.

"Good girl!" Art laughs. "I trained you --" he's obviously about to say "well," but thinks of a better word and corrects himself on the fly. He finishes instead with, "maliciously."

The poster corner has come unstuck again. I put it back up, smooth the tape down carefully, and go home.